The generic wear and tear or accumulated damage theories
attempt only to explain human aging and have difficulty explaining the wide
differences in life span observed between similar species.

The major non-programmed theories (mutation accumulation,
antagonistic pleiotropy, disposable soma) attempt only to explain a single
observation: the variation in life span between gradually aging mammals.

Programmed (adaptive) aging theories suggest the existence of a complex
life span regulation system and provide explanations for a wide variety of
observations as shown below.